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1939 Matchless G3 No Oil Pressure

Hi guys my 1939 G3 won't pump any oil and it never has since I've owned it.
History is last used in 1973, I bought it about 5 years ago as almost complete but non runner, I've been recomisioning it & finding / making all the correct parts since then before I strip and restore.
OK the oil tank is clean, the oil pipes are clean & allow the oil to flow out the bottom, the oil exits the pump housing via the 3 screws in the crank case, the square end caps have been removed & the pump rotates while going in & out but no oil will come out the pipe at the front that goes up to the head & no oil is going into the crankcase so nothing is returning back into the tank.
I've wasted a lot of time on this problem & can't see the wood for the trees.

email (option): ian.air.pilot@hotmail.com

Re: 1939 Matchless G3 No Oil Pressure

I've been reading lots & lots of Forum posts on other sites, would I be right in thinking that the pump needs to be 'primed' buy pouring 1/2 a pint of oil or so down the pushrod tubes to prime the pump & give it something to start with ? I've now given up for the night so not about to go out to the workshop to test the theory ?

email (option): ian.air.pilot@hotmail.com

Re: 1939 Matchless G3 No Oil Pressure

How many times did you turn the engine over until deciding the pump is not working? The AJS/Matchless pump in the single cylinder bikes does not move much oil compared to a gear pump. I sometimes wonder how the bike even runs with so little oil moving around the engine.

Have you taken the pump out of the engine to check for wear on the drive pin? This is usually the only part that wears. If worn the pump shaft won't move back and forth enough to pump oil. If you take off the pump end plates and remove the drive pin, you can push the pump shaft out the back of the engine. At that point oil should flow out at a pretty good rate. If not something is blocked in the feed line.

Another thing to look for is over the years changes were made to the timing side shaft gear and the associated pump shaft gear teeth. The can't be a mismatched set.

I have both AJS and Matchless singles but have not had to work on them in years so this the best I can remember about the pumps.

Re: 1939 Matchless G3 No Oil Pressure

Before oil returns to the top of the oil tank as far as i can remember it has to fill the filter tube first. These pumps pump slow with little volume, so it would be a while before oil is seen at the return pipe in the tank. Oil needs to be in the bottom of the crankcase for the pump to pick it up. You have said the pump is rotating and moving backwards and forwards. Try priming the crankcase and taking the return pipe off the bottom of the oil tank and watching the top of the pipe as it only has to fill it before you see any return oil.

Re: 1939 Matchless G3 No Oil Pressure

couple of things you could try and check. make sure the pump gear teeth are ok, with the front oil plate the rocker pipe bolts to removed, turn the engine and check that the pump moves or Oscillating all the way to the edge of the engine case and goes back.
put oil in the return outlet on the oil, i use a triggered oil can. check the oil filer maybe clean out in petrol.
another thing, with the oil drain bolt removed, inside the engine directly above the filler hole theres a small hole in the casting, check to se if its clear with a bit of wire or blow it through with air gun. normally if this is blocked the engine would fill with oil as its the scavenge pipe if you like and also part of the oil return.
hope this helps

thanks, barry

Re: 1939 Matchless G3 No Oil Pressure

Some additional items to check.
If the pump guide pin has any ware at the point that it engages with the pump then oil will not get up to the head.if there is any flat spot on th3 pin then replace it.
Make sure you have the correct reciprocating pump fitted and not the later pump as they are not interchangeable
Make sure the hole in the front end plate allowing the oil to be pumped up to the head is not blocked and the the gasket paper does not cover it over.
Make sure there is oil in the sump by squirting oil down the pushrod tubes
Prime the system by removing the cap over the filter and filling the tube with oil. Also use an oil can to back fill the return pipe by squirting oil down the return hole in the tank.
Make sure you do not have the return and feed pipe the wrong way around.
I always get on my bikes and ride them around the block before I check that oil is returning to the tank as it takes ages.

Let us know how you get on. JT

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